JPH11349878A - Ink jet print ink set with reduced bleeding and method for reducing ink bleeding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink set which gives a print with a reduced bleeding between a color ink and a black ink on plain paper by using a black ink contg. an anionic pigment and a color ink contg. a colorant and a cation source selected from among cationic surfactants, cationic salts, and mixtures thereof. SOLUTION: The black pigment used in the black ink is a self-dispersible anionic pigment, including all the water-dispersible anionic black pigments chemically modified for ink jet printing. The color ink contains at least one colorant, dye, or pigment, and an aq. color pigment, such as a sulfonate or carboxylate, is pref. used. The color ink contains about 0.5-5 wt.% cationic surfactant or about 0.1-7 wt.% cationic salt, which is effective in inhibiting bleed between the black and the color ink. The cationic salt is selected pref. from among tetraalkyl-, tetraaryl-, and tetraalkylarylammonium salts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet ink used for inkjet printing,
More particularly, it relates to ink systems that utilize the addition of cationic salts or surfactants to color inks and black inks based on anionic pigments.

[0002]

BACKGROUND OF THE INVENTION Thermal inkjet printers offer a lower cost, higher quality, and relatively noise-free alternative to other types of printers used with computers. This printer employs a resistive element in a chamber with an outlet for ink entering from a plenum. The plenum is connected to an ink storage container. A plurality of such resistive elements are arranged in a printhead in a specific pattern called a primitive. Each resistive element is associated with a nozzle in a nozzle plate through which ink is ejected toward the print medium. An assembly of a printhead and a container together constitutes an ink-jet pen.

[0003] In operation, each resistive element is connected to a microprocessor through a conductive line, in which state the current carrying signal causes the selected element or elements to heat up. The heating creates ink bubbles in the chamber that are ejected through the nozzles toward the print media. In this method, the plurality of resistive elements in a given primitive are energized in a particular order to form alphanumeric characters, fill an area, and provide other printing functions on the media.

[0004] When performing multicolor printing on bond paper, copy paper, and other media, many ink-jet inks can bleed.
Bleed occurs when colors mix on and within the paper being printed. The term "bleed" as used herein is defined as follows: when two different color inks are printed adjacent to each other, the boundary between the two colors is sharp. Desirably, it is a borderline and there is no penetration of one color into the other. As one color enters the other, the border between the two colors becomes jagged. This is called bleed.

This is in contrast to the use of this term in the prior art, which often defines "bleed" in the context of a single color ink entering along the fibers of a paper.

Conventional solutions to bleed largely involve the use of a heated platen or other heating source and / or specialty paper. A heated platen adds cost to the printer. With the solution of using specialty paper,
Only single paper, which is more expensive than plain paper, can be used. Another method of bleed reduction relates to increasing the penetration of ink into the interior of the paper.
Increasing the penetration decreases the edge sharpness (this degrades the print quality of the ink). Nevertheless, because color text quality is less important, this method is acceptable for printing color inks. However, print quality is important for black ink.
Therefore, an alternative bleed control mechanism is needed.

US Pat. No. 5,428,383 discloses a method of controlling bleed in multicolor ink jet printing involving the use of a polyvalent metal salt as a precipitant in the first ink composition. This precipitant is designed to react with the colorant in the second ink composition.

A solution to the specific problem of bleed between black and yellow is disclosed in US Pat. No. 5,198,023. Here, multivalent cations such as calcium chloride and magnesium chloride are added to the yellow cation ink at a concentration ranging from about 1 to about 10% by weight to prevent bleeding between the yellow and black inks. However, it has been found that the addition of large amounts of multivalent cations to the thermal ink-jet ink composition can induce precipitation of the dye salt and requires further adjustment of the ink composition.

US Pat. No. 5,518,534 discloses the use of a first ink having a pigment dispersant and a second ink containing a salt of an organic or mineral acid. Here, the salt reacts with the first ink to reduce bleed between the inks. However, in this case, the pigment requires the presence of a dispersant and both inks must have the same ionic properties.

[0010] The bleed control method is disclosed in US Patent No. 5,730,790.
It is also disclosed in the issue. The inkjet ink comprises at least one dye-based ink composition and at least one dye-based ink composition.
And two pigment-based inks. The dye-based ink also includes a cationic surfactant,
Pigment-based inks include a negatively charged dispersant.

Another method of reducing bleed between ink jet inks involves using a pH-sensitive dye as disclosed in US Pat. No. 5,181,045. The patent discloses an ink having a pH-sensitive dye that prevents bleeding to adjacent inks having the appropriate pH. Bleeding of the ink with the pH-sensitive dye is prevented by making the dye insoluble on the page by contact with an adjacent ink of the appropriate pH. In this method, to completely control bleed,
It is essential that the pH difference be about 4-5. Thus, a pH of 4 or less will be required to effectively remove bleed from pH-sensitive inks having a typical pH of about 8.

US Pat. No. 5,785,743 is based on the above-cited US Pat. No. 8,181,045, but in contrast to the pH-sensitive ink composition, the organic acid component in the so-called target inkjet ink composition. Is added.
With organic acid components, the pH difference required to control bleed is about 3
It becomes smaller below.

Although the various solutions described above have been successful, when printed on plain paper, they do not exhibit bleed as defined herein, and have a relatively long shelf life and ink. There remains a need for ink compositions for inkjet printing that have the other properties of.

[0014]

SUMMARY OF THE INVENTION In accordance with the present invention, bleed between color and black has been reduced by using at least one anionic pigment in the black ink and at least one cationic surfactant or salt in the color ink. An ink set is provided, ie a set of inks of several types. This ink formulation is extremely effective in reducing bleed between black and color without the need for rapid penetration of the black ink. Color inks can include nonionic, cationic, or anionic dyes.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An important consideration in considering the problem of bleed mitigation involving a set of cyan, magenta, yellow and black inks that results in all color combinations when printing in various combinations. The point of interest is that the yellow ink is visually the worst bleed color due to the contrast between yellow and any of the other inks, especially black. That is, if all other conditions are the same, bleed is less visually noticeable between any combination of cyan, magenta, and black ink than between yellow and black inks. Therefore, bleeding between the yellow and black inks of the ink set must be given special importance.

[0016] In one approach, the black pigment used in the black ink is a self-dispersing anionic pigment. The aforementioned anionic pigments suitable for use herein include all chemically modified water-dispersible anionic black inks known for inkjet printing. Due to these chemical modifications, the pigment precursors, including all organic pigments, become water dispersible.
bility). Under typical chemical treatments, the resulting surface consists of carboxylated and / or sulfonated functional groups. In commercially available anionic pigments, the anion pigment is typically associated with Na ⁺ , Li ⁺ , K ⁺ , and NH ₄ ⁺ cations, but any suitable pair of ions can be used. Many suitable water-dispersible black pigments include Ca
It is commercially available from colorant suppliers such as bot Corp. and Orient Chemical. See U.S. Patent Nos. 5,630,868 and 5,571,311 for a discussion of modified carbon pigments.

[0017] In another embodiment herein, the black pigment is dispersed in the ink composition with the aid of a dispersant.
The black pigment includes any black pigment dispersed with a dispersant having anionic functionality, such as the polymer Joncryl, available from SC Johnson Polymer of Racine, Wisconsin, USA. Of course, any other dispersant that exhibits an anionic charge can be used in the practice of the present invention. For a more complete discussion of black pigments and anionic dispersants, see U.S. Pat.
See Nos. 5 and 5,785,743.

The following pigments are examples of black pigments commercially available from Columbian: Raven 7000, Raven 5750, Ra
ven 5250, Raven 5000, Raven 3500. The following pigments are commercially available from Degussa: Color Bla
ck FW 200, Color Black FW 2, Color Black FW 2V, Co
lor Black FW 1, Color Black FW 18, Color Black S 1
60, Color Black S 170, Special Black 61, Special B
lack 5, Special Black 4A, Special Black 4.

Color inks-Color inks contain at least one colorant, usually a dye or pigment. The dye or pigment may be non-ionic, cationic, anionic, or a mixture thereof. Any of the color dyes or pigments known for ink jet printing can be used in the practice of the present invention.

The following pigments are useful in the practice of the present invention. However, it is a matter of course that there is no intention to limit the present invention to those listed below. The following pigments are available from BASF: Paliogen Orange, Heliogen Blue L 6901
F, Heliogen Blue NBD 7010, Heliogen Blue K 7090, He
liogen Blue L 7101F, Paliogen Blue L 6470, Helioge
n Green K 8683, Heliogen Green L 9140. The following pigments are available from Cabot: Monarch 1400,
Monarch 1300, Monarch 1100, Monarch 1000, Monarch
900, Monarch 880, Monarch 800, Monarch 700. The following pigments are available from Ciba-Geigy: Chromoph
tal Yellow 3G, Chromophtal Yellow GR, Chromophtal
Yellow 8G, Igrazin Yelolow 5GT, Igralite Rubine 4B
L, Manastral Magenta, Monastral Scarlet, Monastral
Violet R, Monastral Red B, Monastral Violet Maroo
n B. The following pigments are available from Degussa: Printex U,
Printex V, Printex 140U, Printex 140V. The following pigments are available from DuPont: Tipure ^(R) R-
101. The following pigments are available from Heubach: Dalamar Yel
low YT-858-D, Heucophthal Blue G XBT-583D. The following pigments are available from Hoechst: Permanent Y
ellow GR, PermanentYellow G, Permanent Yellow DHG,
Permanent Yellow NCG-71, Permanent Yellow GC, Han
sa Yellow RA, Hansa Brilliant Yellow 5GX-02, Hansa
Yellow-X, Novoperm ^(R) Yellow HR, Novoperm ^(R) Yell
ow FGL, Hansa Brilliant Yellow 10GX, Permanent Yel
low G3R-01, Hostaperm ^(R) Yellow H4G, Hostaperm ^(R)
YellowH3G, Hostaperm ^(R) Orange GR, Hostaperm ^(R) Sc
arlet GO, Permanent Rubine F6B. The following pigments are available from Mobay: Quindo ^(R) Mag
enta, Indofast ^(R) Brilliant Scarlet, Quindo Red R6
700, Quindo Red R6713, Indofast Violet. The following pigments are available from Sun Chem: L74-1357 Y
ellow, L75-1331 Yellow, L75-2577 Yellow.

In carrying out the present invention, an aqueous color dye may be used. Examples of aqueous dyes include sulfonates and carboxylate salts, especially those commonly used for ink jet printing. Specific examples include: Sulforhodamine B (sulfonate), Acid B
lue 113 (sulfonate), Acid Blue 29 (sulfonate), Acid Red 4 (sulfonate), Rose Bengal (carboxylate), Acid Yellow 17 (sulfonate), Acid
Yellow 29 (sulfonate), Acid yellow 42 (sulfonate), Acridine Yellow G (sulfonate), Nit
ro Blue Tetrazolium Chloride Monohydrate or Nitro
BT, Rhodamine 6G, Rhodamine 123, Rhodamine B, Rhod
amine B Isocyanate, Safranine O, Azure B, Azure B
Eosinate, Basic Blue 47, Basic Blue 66, Thiflacin
T (Basic Yellow 1) and Auramine O (Basic Yellow 2)
(All are commercially available from Aldrich Chemical Company).

Cationic Reagent-The color ink also contains a cationic surfactant or cationic salt. The cation salt is
Preferably, it is selected from tetraalkyl or tetraaryl or tetraalkylaryl ammonium salts.
The alkyl moiety in the cationic salt can be any straight or branched hydrocarbon consisting of a saturated or unsaturated chain. Preferred alkyl units are selected from the group consisting of methyl, ethyl, butyl, hexyl, octyl, decyl, dodecyl and mixtures thereof. Preferred aryl units are selected from the group consisting of phenyl, benzyl, or alkylaryl subunits of 18 carbons or less. An example of a suitable cation is the tetrabutylammonium cation. Another example is the benzyltriethylammonium cation. The tetraalkylammonium salt binds to a counterion, which is an anion. The counter ion is preferably selected from the group consisting of halogen ions, bisulfite ions, bisulfate ions, dihydrogen phosphate ions, nitrate ions, nitrite ions, and mixtures thereof.

The concentration of the cation salt is expressed in terms of% by weight of the ink composition.
In the range of about 0.1 to about 7, preferably about 1 to about 3. About 0.
Concentrations below 1% by weight have been found to be ineffective in controlling bleed from black to color.

Alternatively, the color inks employed herein may include a cationic surfactant. The cationic surfactant is included in the ink composition in an amount of about 0.5 to about 5% by weight.
Must be present at a concentration in the range Preferably, the cationic surfactant is used in the ink at a concentration of about 3% by weight. It is contemplated that any cationic surfactant known to be useful in ink-jet ink compositions may be employed in the practice of the present invention. Examples of suitable cationic surfactants include, but are not limited to, polypropoxy quaternary ammonium acetates and polypropoxy quaternary ammonium chlorides. These surfactants are available from WITCO Co
Commercially available from rporation as the Emcol series. The component of the cationic surfactant may include a mixture of several suitable cationic surfactants.

Examples of counterions which can be combined with the useful cationic surfactants herein include acetate, formate, chloride, gluconate, succinate, tartrate, glutarate, malonate and malonate. Ion, carboxylate ion, fumarate ion, malate ion, sebacate ion, adipate ion, stearate ion, oleate ion, laurate ion, benzoate ion and citrate ion.

Other cationic surfactants, such as substituted amine oxides, are also useful in practicing the present invention. For a list of amine oxides, see "Bleed Alleviation Using
See U.S. Patent No. 5,106,416 entitled "Zwitterionic Surfactants and Cationic Dyes." A specific example of an amphiphile / surfactant that can be suitably used in the practice of the present invention is isohexadecyl ethylene oxide.
20, SURFYNOL CT-111, TERGITOL 15-S-7, and N, N-dimethyl-N-dodecylamine oxide, N, N-dimethyl-N-tetradecylamine oxide, N, N-dimethyl-N-hexadecyl Amine oxides, such as amine oxides, N, N-dimethyl-N-octadecylamine oxide and N, N-dimethyl-N- (Z-9-octadecenyl) -N-amine oxide.

Organic Acids-Optionally, the color dyes herein may further comprise an organic acid component to aid bleed control. It has been found that by using a relatively small amount of this organic acid, the effect of suppressing bleeding of the cationic salt or cationic surfactant is enhanced. Therefore, the organic acid, if present, may be present in an amount of about 0.5% to about 4%, preferably about 1% to about 4% by weight of the ink composition.
It should be in the range of about 3% by weight, more preferably about 2% by weight. Examples of organic acids that can be suitably used in the practice of the present invention include one, two, or more functional acids. Preferably one of the following types of organic acids is used: polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid , Lactic acid, sulfonic acid, and orthophosphoric acid and their derivatives.

All concentrations herein are expressed in weight percent unless otherwise specified. The purity of all components is the concentration used in normal commercial practice as an inkjet ink.

Inkjet Vehicle-The ink contains a vehicle in addition to the colorant and the cationic surfactant or salt described above. Ink and For a discussion about the ^{nature, The Printing Manual, 5 th ed} . Leach et
al. (Chapman and Hall, 1993). Also,
U.S. Patent Nos. 2,833,736, 3,607,813, 4,104,061
See also Nos. 4,770,706 and 5,026,755.

Typical formulations of inks useful in the practice of the invention include one or more cosolvents (0 to about 50% by weight), one or more water-soluble surfactants / amphiphiles (0
To about 40% by weight, preferably about 1 to about 5% by weight) (these are added to the vehicle and are further added to any cationic surfactant used in color inks for bleed control); One or more high molecular weight colloids (0-
About 3% by weight), and water (balance).

One or more co-solvents may be added to the vehicle during ink formulation. The types of co-solvents used in the practice of the present invention are of course, but not limited to, aliphatic alcohols, aromatic alcohols, diols, glycol ethers, poly (glycol)
There are ethers, caprolactams, formamides, acetamides, and long-chain alcohols. Examples of compounds used in the practice of the invention are, of course, but not limited to, primary aliphatic alcohols of 30 carbons or less, primary aromatic alcohols of 30 carbons or less, 30 carbons or less.
Secondary aliphatic alcohols of up to 30 carbons, secondary aromatic alcohols of up to 30 carbons, 1,2-alcohols of up to 30 carbons, 1,3-alcohols of up to 30 carbons, 1 of up to 30 carbons ,Five-
Alcohols, ethylene glycol alkyl ethers, propylene glycol alkyl ethers, poly (ethylene glycol) alkyl ethers, relatively higher homologs of poly (ethylene glycol) alkyl ethers, poly (propylene glycol) alkyl ethers, poly There are relatively higher homologues of (propylene glycol) alkyl ethers, N-alkyl caprolactams, unsubstituted caprolactams, substituted formamides, unsubstituted formamides, substituted acetamides, and unsubstituted acetamides. Specific examples of the co-solvent preferably used in the practice of the present invention include, but are not limited to, 1,5-pentanediol, 2-pyrrolidone, 2-
Ethyl-2-hydroxymethyl-1,3-propanediol, diethylene glycol, 3-methoxybutanol, and 1,3-
There is dimethyl-2-imidazolidinone. Cosolvent concentration is 0
To about 50% by weight, preferably from about 0.1 to 1%.
It is in the range of 5% by weight.

In preparing the ink medium, water-soluble surfactants may be used. For convenience, examples of surfactants are divided into two categories: (1) non-ionic and amphoteric and (2) ionic. The former types include TERGITOL (alkyl polyethylene oxides commercially available from Union Carbide), TRITON
(Alkylphenyl polyethylene oxide surfactants commercially available from Rohm & Haas Co.), BRIJ, PLLURONIC (polyethylene oxide block copolymers), SURFYNOL
(Acetylene-type polyethylene oxides commercially available from Air Products), POE (polyethylene oxide) esters, POE diesters, POE amines, protonated POE amines, POE amides, and dimethicone copolyols.

Various types of additives may be employed in the ink without departing from the requirements of the present invention to optimize the properties of the ink composition for use in a particular application. For example, as is well known to those skilled in the art, biocides may be included in the ink composition to inhibit the growth of microorganisms, and include sequestering agents such as EDTA to reduce the deleterious effects of heavy metal impurities. The pH of the ink may be adjusted using a buffer solution. Viscosity modifiers and other known additives such as other acrylic or non-acrylic polymers may be added to improve various properties of the ink composition as desired.

[0034] The inks are formulated by combining the various components of the vehicle and mixing them with the colorants and cationic bleed control additives disclosed herein.

[0035]

Industrial applicability The inclusion of cationic surfactants or salts in color inks and the inclusion of an anionic black pigment in ink sets is expected to be useful for inks used in ink jet printing. .

[0036]

EXAMPLE Two different black pigment inks A and B were printed side by side with three color inks (yellow). Of the color inks, the first ink (color ink A) contains only succinic acid, the second ink (color ink B) contains only tetrabutylammonium nitrate, and the third ink (color ink C) Contained a mixture of succinic acid and tetrabutylammonium nitrate.

The formulation of black ink A includes Cabot Corporatio
n containing CABOJET 300 and a self-dispersible carbon black pigment.

The black ink B formulation contained a polymer-dispersed carbon black pigment.

The formulation of Color Ink A included pentanediol, 2-pyrrolidone, 15% by weight co-surfactant (cosu
rfactant), containing 7% by weight of succinic acid.

The formulation of Color Ink B included pentanediol, 2-pyrrolidone, 15% by weight co-surfactant, and
It contained 3% by weight of tetrabutylammonium nitrate.

The formulation of Color Ink C contained pentanediol, 2-pyrrolidone, 15% by weight cosurfactant, 3% by weight tetrabutylammonium nitrate, and 2% by weight succinic acid.

A standard test pattern of black ink and yellow ink was executed for each of black ink and color ink.
The results for the self-dispersed colored ink and the polymer-dispersed black ink were similar.

Each of the standard test pattern for the combination of the black ink A and the color ink A and the standard test pattern for the black ink B and the color ink A include the black ink in the yellow ink with a visible blur at the ink boundary. There was evidence of bleeding.

Both the standard test pattern for the combination of black ink A and color ink B and the standard test pattern for the combination of black ink B and color ink B bleed from the black side to the color side in comparison with color ink A. This indicates that the degree of suppression has been improved overall, and the visible blur at the ink boundaries has been significantly reduced.

In the standard test pattern for the combination of black ink A and color ink C and the standard test pattern for the combination of black ink B and color ink C,
Each shows that the degree of suppression of bleeding from black to the color side is remarkably improved as compared with the color ink A or B, sharpness is remarkably improved, and visible at the ink boundary. The blur is less.

Examples of the embodiments of the present invention will be listed below.

Embodiment 1 In an inkjet ink set for inkjet printing comprising at least one color ink and at least one black ink, the black ink comprises at least one anionic pigment, and the color ink comprises: An ink-jet ink set comprising: one colorant; and b) at least one cation source selected from the group consisting of cationic surfactants, cation salts and mixtures thereof.

[Embodiment 2] The ink-jet ink set according to embodiment 1, wherein the black ink contains the pigment and a dispersant.

[Embodiment 3] The ink-jet ink set according to embodiment 1, wherein the anionic pigment is a self-dispersing pigment.

[Embodiment 4] The ink-jet ink set according to embodiment 3, wherein the anionic pigment contains an anionic functional group selected from the group consisting of carboxylate, sulfonate and mixtures thereof. .

[Embodiment 5] The ink-jet ink set according to embodiment 1, wherein the color ink contains 0.5 to 5% by weight of a cationic surfactant.

[Embodiment 6] The ink-jet ink set according to embodiment 1, wherein the color ink contains 0.1 to 7% by weight of a cationic salt.

[Embodiment 7] The cation salt is a tetraalkylammonium salt, and the alkyl moiety is a linear or branched hydrocarbon containing a saturated or unsaturated chain, or an aromatic subunit having 18 or less carbon atoms. The ink-jet ink set according to claim 6, wherein:

[Embodiment 8] The inkjet ink set according to Embodiment 1, wherein the color ink further contains 1 to 3% by weight of an organic acid, preferably succinic acid.

Embodiment 9 In a method for reducing color bleeding between black ink and color ink, at least one
Formulating said black ink comprising two anionic pigments; a) at least one colorant; and b) at least one cation source selected from the group consisting of cationic surfactants, cation salts and mixtures thereof. And a step of preparing the color ink, the method comprising:

[Embodiment 10] The color ink is used in an amount of 0.1.
Embodiment 10. The method for reducing ink bleed according to Embodiment 9, comprising 5 to 5% by weight of a cationic surfactant.

[Embodiment 11] The cation salt is a tetraalkylammonium salt, and the alkyl moiety is a linear or branched hydrocarbon comprising a saturated or unsaturated chain or
11. The method for reducing ink bleeding according to embodiment 10, wherein the aromatic subunit is carbon or less.

[Embodiment 12] The method according to Embodiment 11, wherein the cation salt is selected from the group consisting of tetrabutylammonium nitrate, benzyltriethylammonium nitrate, and a mixture thereof.

[Thirteenth Embodiment] The method for reducing ink bleed according to the ninth embodiment, wherein the black ink contains the pigment and the dispersant.

[Embodiment 14] The method according to Embodiment 9, wherein the anionic pigment is a self-dispersing pigment.

[Embodiment 15] The color ink is 1 to 3
10. The method for reducing ink bleed according to claim 9, comprising an organic acid, preferably succinic acid, by weight.

Claims (2)

[Claims] 1. An inkjet ink set for inkjet printing comprising at least one color ink and at least one black ink, wherein the black ink comprises at least one anionic pigment, wherein the color ink comprises: a) at least one color An ink jet ink set comprising an agent and b) at least one cation source selected from the group consisting of cationic surfactants, cation salts and mixtures thereof. 2. A method for reducing color bleeding between black and color inks: formulating said black ink comprising at least one anionic pigment; a) at least one colorant; and b) cation. Formulating said color ink comprising at least one cation source selected from the group consisting of surfactants, cation salts and mixtures thereof.